In recent years, a measurement technology by which a vehicle exterior target sight is captured by a camera or the like mounted on a car and this captured image is subjected to image processing to obtain a distance from the car to a target object has been adopted as leading means (for example, refer to Japanese Unexamined Patent Application Publication No. 5-114099 (PTL 1)).
This distance measurement technology with an image is roughly classified into a technology by which a distance to a target object is estimated by using a relation with a camera position from a monocular image and a technology by which a distance to a target object is obtained by using triangulation principles from a plurality of images photographed by a plurality of cameras.
Among them, with the measurement technology by which a distance is obtained by using triangulation principles from a plurality of images, the distance is obtained from relative shift of positions of a same object in left and right images, so that it is possible to obtain the distance accurately.